Scrape cells off the plates and transfer to microcentrifuge tubes. Keep on ice.

Sonicate samples on ice three times for 5 seconds each.

Microcentrifuge for 10 minutes at 4°C, 14,000 x g, and transfer the supernatant to a new tube. If necessary, lysate can be stored at –80°C.

C. Immunoprecipitation

Take 200 μl cell lysate and add 10 µl of the immobilized antibody, incubate with rotation overnight at 4°C.

Wash pellet by using magnetic rack to pellet beads, then discard supernatant once completely clear and add 500 µl of 1X cell lysis buffer, vortex to resuspend and wash the beads, repeat 4 more times for a total of 5 washes.

Proceed to sample analysis by western blotting or kinase activity (section D).

For Analysis by Kinase Assay

Wash pellet by using magnetic rack to pellet beads, then discard supernatant once completely clear and add 500 Âµl of 1X kinase buffer, vortex to resuspend and wash the beads, repeat 1 more time for a total of 2 washes. Keep on ice during washes.

Akt, also referred to as PKB or Rac, plays a critical role in controlling survival and apoptosis (1-3). This protein kinase is activated by insulin and various growth and survival factors to function in a wortmannin-sensitive pathway involving PI3 kinase (2,3). Akt is activated by phospholipid binding and activation loop phosphorylation at Thr308 by PDK1 (4) and by phosphorylation within the carboxy terminus at Ser473. The previously elusive PDK2 responsible for phosphorylation of Akt at Ser473 has been identified as mammalian target of rapamycin (mTOR) in a rapamycin-insensitive complex with rictor and Sin1 (5,6). Akt promotes cell survival by inhibiting apoptosis through phosphorylation and inactivation of several targets, including Bad (7), forkhead transcription factors (8), c-Raf (9), and caspase-9. PTEN phosphatase is a major negative regulator of the PI3 kinase/Akt signaling pathway (10). LY294002 is a specific PI3 kinase inhibitor (11). Another essential Akt function is the regulation of glycogen synthesis through phosphorylation and inactivation of GSK-3α and β (12,13). Akt may also play a role in insulin stimulation of glucose transport (12). In addition to its role in survival and glycogen synthesis, Akt is involved in cell cycle regulation by preventing GSK-3β-mediated phosphorylation and degradation of cyclin D1 (14) and by negatively regulating the cyclin dependent kinase inhibitors p27 Kip1 (15) and p21 Waf1/Cip1 (16). Akt also plays a critical role in cell growth by directly phosphorylating mTOR in a rapamycin-sensitive complex containing raptor (17). More importantly, Akt phosphorylates and inactivates tuberin (TSC2), an inhibitor of mTOR within the mTOR-raptor complex (18,19).